For various types of conduits, it is often necessary to remove adherent material which has built up within the inner surface during usage. Paint delivery systems often require such a cleaning. Paint deposits generally adhere to the inner surface of the tubes or conduits of the paint delivery system and pose a problem during cleaning.
Paint delivery systems are widely used to provide paint coatings on a large variety of articles of manufacture. Often a single delivery system is used to apply a multitude of paint finishes and colors. To efficiently retool a delivery system from one paint color to the next, the need arises for a rapid method of cleaning the conduit elements of the system.
With paint delivery systems it is desirable that the cleaning method fully remove all residue from the tube so as not to interfere with subsequent coatings.
The various former methods for cleaning the inner surfaces of a tube or conduit can be classified into three categories:
1) solvent methods where the adherent material is chemically dislodged from the inner surface;
2) mechanical removal methods such as scraping, where the adherent material is forcibly extracted from the inner surface; and
3) blasting techniques involving highly pressurized mechanisms that blast a specified area to remove adherent material with the use of pressure.
Mechanical techniques are often limited in their scope of usage. These mechanical techniques require that the device used be of a size and shape to fit within the conduit. Thus mechanical devices are too restrictive for many tubes or conduits. Blasting techniques require complicated machinery and once again the machinery has to be able to fit within the conduit itself to operate, similar problems then exist with this method as with the use of mechanical devices. In contrast, solvent methods have the widest range of application, as the type or shape of conduit poses no barrier.
Typically the surface to be cleaned dictates the type of cleaning method that can be employed. Ideally, however, a delicate method of cleaning would prevent damage or destruction to a variety of underlying substrates and the use of a solvent removal system facilitates cleaning conduits of various shapes and sizes.
In the past, cleaning compositions containing various abrasive materials have been used. The use of an abradant material increases the effectiveness of the composition in removing undesired matter from the surface being cleaned. However, along with the benefits there have also been associated certain problems. Previous attempts at using inorganic materials as an abrasive particulate material have come to no avail. For example, U.S. Pat. No. 4,821,467 ("'467 patent") discloses a control system for liquid propelled abrasive cleaning. The '467 patent describes an abrasive cleaning system comprising a pressurized stream of water and propelled sand particles. Using such an embodiment of an inorganic material poses many problems. The use of such abrasives tend to be hard and therefore can damage the pump components or underlying substrate of the surface to be cleaned. Additionally, sand is a relatively dense material which separates out of the cleaning fluid rather than staying in situ.
It is also known to use mica as an abrasive particle within a cleaning system. The use of mica presents the same problem as those associated with the use of sand. Again, such abrasives are usually hard therefore they raise the possibility of damaging the pump components or the underlying substrate being cleaned. Additionally mica, like sand, is a relatively dense material which separates out of the cleaning fluid rather than staying in situ. Keeping the mixture together is thus an obstacle with this type of inorganic material.
In the arena of organic materials, prior art includes U.S. Pat. No. 4,968,447 which describes the use of an organic material dispersed within a solvent mixture. The patent relates to a method of cleaning employing an organic polymeric material dispersed within a liquid vehicle. Organic polymeric materials do not provide sufficient abrasive characteristics and therefore the solvent system takes longer to clean a given tube.
N-methyl-2-pyrrolidone (NMP) has been used as a paint stripper per se. U.S. Pat. No. 5,015,410 describes a paint stripper composition containing NMP, aliphatic and aromatic hydrocarbons. The patent states that the benefits of using NMP include that the resultant paint strippers have a low volatility, and low toxicity. The problem lies in that a purely liquid based remover does not have any abrasive properties and therefore more washes are required to strip the paint from any given surface. In sum, the use of an exclusively NMP solvent remover is only moderately effective.
A need exists, therefore, for a cleaning composition that effectively cleans the tubes or conduits without damaging the surface to be cleaned. More particularly, a need exists for a cleaning composition which can clean similar to abradant materials without the harsh side effects.
In accordance, the present invention provides the cleaning properties characteristic of abradant materials with improved cleaning capability but without harsh side effects which may result in damage to pump components or the underlying surface to be cleaned.